Introduction Prostate specific membrane antigen (PSMA) expression has been demonstrated in tumor neovasculature of many solid tumors, including hepatocellular carcinoma (HCC). The purpose of this study is to evaluate PSMA expression in patients with HCC. Materials and Methods Nineteen HCC patients who underwent 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET) as part of restaging procedure also underwent 68Ga-PSMA PET. 18F-FDG PET and 68Ga-PSMA findings were compared visually as well as quantitatively using maximized standardized uptake values (SUVmax). Results FDG was positive in 15 patients while 16 patients demonstrated PSMA expression. The only extrahepatic finding was one metastatic lymph node detected by both tracers. Mean SUVmax of liver lesions on FDG PET/CT was 8.3 ± 2.3 and mean tumor to background ratio was 2.3 ± 1.5. Respective values for 68Ga-PSMA PET/CT were 17.4 ± 9 and 3.3 ± 2.2. On visual and quantitative evaluation uptake was higher with PSMA in nine patients and higher with FDG in four patients. PSMA and FDG activity were similar in three patients. One of the FDG positive patients was PSMA negative whereas two patients were PSMA positive but FDG negative. Heterogeneous uptake pattern was observed in three patients. Comparison of mean SUVmax and T/B values between PET studies revealed no statistically significant difference (P > 0.1). The mean survival was 25 months (range: 18–32 months) and SUVmax of PSMA (P = 0.05) and FDG (P = 0.012) showed medium strength of correlation with overall survival. Conclusion PSMA expression in advanced HCC can be demonstrated by 68Ga-PSMA PET but is not superior to FDG PET however it could be useful for identifying patients with limited therapeutic options.

Herein we present 2 mCRPC (metastatic castration-resistant prostate cancer) patients who underwent 68Ga-PSMA PET/CT for PSMA-targeted radioligand therapy eligibility. Prior studies have noted aggressive clinical behavior and poor prognosis associated with discordant FDG positivity and low PSMA expression. Accordingly, the patients also underwent 18F-FDG PET/CT, which revealed intratumoral heterogeneity. Therefore, an additional PET/CT targeting fibroblast activation proteins (FAPs) using 68Ga-FAPI-04 was performed to assess the potential for an FAP-targeted therapy. This report highlights the theranostic potential of FAP imaging in mCRPC, particularly in patients with heterogeneous tumor phenotypes.

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